Optomechanical non-reciprocal device

ABSTRACT

There is set forth herein an optomechanical device which can comprise a first mirror and a second mirror forming with the first mirror a cavity. In one aspect the first mirror can be a movable mirror. The optomechanical device can be adapted so that the first mirror is moveable responsively to radiation force.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage application under 35 U.S.C. §371 ofPCT Application No. PCT/US2010/024806, filed Feb. 19, 2010, entitled“Optomechanical Non-Reciprocal Device,” which claims priority to U.S.Application No. 61/153,913, filed Feb. 19, 2009, entitled“Optomechanical Non-Reciprocal Device,”,” which is incorporated hereinby reference.

FIELD OF THE INVENTION

This invention relates generally to optomechanical devices, and morespecifically to optomechanical devices capable of exhibitingnon-reciprocal behavior.

BACKGROUND OF THE INVENTION

Recent work in optomechanics, enabled by advances in optical microcavities and nano-electro-mechanical systems, has shown tremendouspotential for new classes of micro scale devices and phenomena.

Traditional methods for providing non reciprocal devices rely onmagneto-optic media, optically active media, or electro-optic crystals.According to a non-reciprocal optical system based on magneto-opticalgyrotropy, a forward propagating right circularly polarized mode can betransformed by the operation of time reversal to a backward propagatingmode that is also right circularly polarized. In a non-reciprocaloptical system based on electro-optic crystals, non-reciprocity can takethe form of two-wave mixing and can incorporate a phase grating that canbe displaced from a fringe pattern generated by two waves being mixed.

SUMMARY OF THE INVENTION

There is set forth herein an optomechanical device which can comprise afirst mirror and a second mirror forming with the first mirror a cavity.In one aspect the first mirror can be a movable mirror. Theoptomechanical device can be adapted so that the first mirror ismoveable responsively to radiation force.

BRIEF DESCRIPTION OF THE DRAWINGS

The features described herein can be better understood with reference tothe drawings described below. The drawings are not necessarily to scale,emphasis instead generally being placed upon illustrating the principlesof the invention. In the drawings, like numerals are used to indicatelike parts throughout the various views.

FIG. 1 is a side schematic view of an optomechanical device having anoptical cavity.

FIG. 2 is a side view illustrating fabrication detail for theoptomechanical device of FIG. 1.

FIG. 3 is a side schematic view of an optomechanical device operative asan isolator.

FIG. 4 is a transmittance plot for the optomechanical device as shown inFIG. 3.

FIG. 5 is a side schematic view of an optomechanical device operative toselectively pass light at low power.

FIG. 6 is a transmittance plot for the optomechanical device as shown inFIG. 5.

FIG. 7 is a side schematic view of an optomechanical device operative toselectively transmit light at high power.

FIG. 8 is a transmittance plot for the optomechanical device as shown inFIG. 6.

FIG. 9 is a side schematic view of an optomechanical device operative toselectively transmit light at intermediate power.

FIG. 10 is a transmittance plot for the optomechanical device as shownin FIG. 9.

FIG. 11 is a perspective schematic view of an optomechanical deviceincluding a plurality of optical cavities arranged in series.

FIG. 12 is a perspective schematic view of an optomechanical deviceincluding a two dimensional array of optical cavities.

FIG. 13 is a schematic view of an optomechanical device including aplurality of stacked arrays.

FIG. 14 is a perspective view of an optomechanical device including aneyewear apparatus incorporating an optical cavity.

FIG. 15 is a top view of an in-line non-reciprocal optomechanicaldevice.

FIG. 16 is a perspective view of the optomechanical device of FIG. 15.

FIG. 17 shows an optomechanical scheme set forth herein, non-reciprocalresponse.

FIG. 18 shows a side view of an optomechanical device for realizingnon-reciprocal transmission spectra.

FIG. 19 shows a top view of the optomechanical device of FIG. 20.

FIG. 20 is a diagram showing a mechanical response of the suspendedmirror for a radiation force corresponding to 100 mW incident power.

FIG. 21 shows an optical transmission through the device for low lightintensities. Reflectivity spectra for the mirrors are shown in dottedlines. Layer thicknesses of the mirrors are slightly offset (5 nm) toallow for a pump probe measurements.

FIG. 22 shows transmission spectra of the device for forward andbackward incidence of light.

FIG. 23 shows a steady state displacement of the movable mirror forforward and backward incidence of light.

FIG. 24 shows transmission spectra of the proposed device for forwardand backward incidence of light when the movable mirror is constrainedat 30 nm displacement to achieve stability on resonance.

FIG. 25 shows mirror displacements for forward and backward incidentlight.

FIG. 26 shows an optomechanical structure set forth herein a Fabry-Perot(FP) cavity with one of the mirrors movable and the other fixed to thesubstrate. The left mirror is reflecting for the pump and probe. Theright mirror is reflecting only for the probe.

FIG. 27 shows an optomechanical device for non reciprocal transmissionsquarter wave Bragy reflectors are formed at either ends of a Siθ₂cavity. The structure is fabricated by attaching two SOI wafers. Braggreflectors are designed such that both the reflectors are reflective forthe probe signal. Only the movable mirror is reflective for the controlpump signal.

FIG. 28 shows reflectivity spectra for the mirrors. The non movablemirror is transparent to the pump beam.

FIG. 29 shows transmission spectrum of the device under no excitation.

FIG. 30 shows transmission spectrum of the device for forward andbackward probe beam excitation.

FIG. 31 shows close up transmission spectra of the device for top(forward) and bottom (backward) incidence of pump beam. When light isincident from top, the cavity is blue shifted. When light is incidentfrom bottom the cavity is red shifted. A shift of 10 nm is assumedconsistent with the mechanical simulations.

FIG. 32 shows a mechanical response of the movable mirror.

FIG. 33 shows an in-plane alternative to an optomechanical device.

DETAILED DESCRIPTION OF THE INVENTION

There is set forth herein an optomechanical device 100 which cancomprise a first mirror 110 and a second mirror 120 forming with thefirst mirror a cavity 200. In one aspect the first mirror 110 can be amovable mirror.

Optomechanical device 100 can be adapted so that first mirror 110 ismoveable responsively to radiation forces resulting from the emission oflight. Radiation force can also be expressed as “radiation pressure,”force per unit area. In the development of optomechanical device 100 itwas determined that if a mass of first mirror 110 is sufficiently small,(e.g., nanoscale) and is appropriately arranged, mirror 110 can moved byradiation force resulting from incident light incident from acommercially available light source. In one embodiment, a light sourcecan be operatively disposed in an optomechanical device including alight source and a cavity. In one embodiment, an optomechanical devicecan be operatively disposed to interact with light from an unknown lightsource.

The force imparted by light beam 10 can be given byF=P/c  [Eq. 1]

Where P is the power of the beam, and c is the speed of light in avacuum. Accordingly, for a light beam emitted by a commerciallyavailable light source, the beam can be expected to impart a force on amechanical object of on order of nN (nanonewtons), which for manyapplications can be ignored. In embodiments set forth herein, movablemirror 110 can be provided in such form (e.g., as a nanoscale apparatus)and can be appropriately arranged as to be movable by radiation forcesresulting from emission of light from a commercially available lightsource. In one embodiment, a sum of forces (net force) on a movablemirror of an optical cavity can include a sum of an incident radiationforce, a reflective radiation force, and a cavity buildup radiationforce.

An aspect of cavity 200 as shown in the embodiment of FIG. 1 is that atransmittivity (transmission) wavelength band (resonance wavelengthband) of cavity 200 is dependant on a relative distance spacing of firstmirror 110 and second mirror 120. A position dependent reflectivelyR(λ,x,t) of a cavity as shown in FIG. 1 as a function of a displacement,x of, mirror 110 can be given by:

$\begin{matrix}{{R\left( {\lambda,x,t} \right)} = {1 - \left\lbrack {\left( \frac{\left| {t_{1}t_{2}} \right|}{\left. {1 -} \middle| {r_{1}r_{2}} \right|} \right)^{2}\frac{1}{1 + {4\left( \frac{\sqrt{\left| {r_{1}r_{2}} \right|}}{\left. {1 -} \middle| {r_{1}r_{2}} \right|} \right)^{2}\sin^{2}\mspace{14mu}{\varphi(x)}}}} \right\rbrack^{1\text{/}2}}} & \left\lbrack {{Eq}.\mspace{14mu} 2} \right\rbrack\end{matrix}$where φ(x) is the phase shift per round trip inside the cavity:

$\frac{1}{2}{{Arg}\left\lbrack {r_{1}r_{2}{\mathbb{e}}^{{\mathbb{i}}\frac{2\pi}{\lambda}{({l - x})}}} \right\rbrack}$and r₁, r_(2 &) t₁, t₂ are the mirror reflectivities andtransmittivities; /is the steady state cavity length.

Accordingly, if input light energy results in a change in relativespacing of the first mirror 110 and the second mirror 120, a shift inthe resonance wavelength band of cavity 200 can be expected. Inoptomechanical devices set forth herein various arrangements of cavitiesincluding a movable mirror responsive to radiation force are provided.In some embodiments described herein, an optomechanical device caninclude an associated light source which has an emission band and/orpower emission characteristics that are complementarily selected withcharacteristics of cavity 200.

In another aspect, a moveable mirror 110 of cavity 200 can be mademoveable by way of a number of alternative mounting structures. Mountingstructures for making a mirror of device 110 movable includecantilevers. Alternate methods of mechanical suspension can be selectedincluding electrical, optical, magnetic levitation, microfluidic.Mirrors 110, 120 in one embodiment can be provided, e.g., by distributedBragg gratings having layers of alternating diffractive indices,photonic crystals, and in-plane mirrors.

A diagram illustrating an exemplary construction of optomechanicaldevice 100 is shown in FIG. 2. Optomechanical device 100 can be formedusing a solid state material platform. In one embodiment, fabrication ofoptomechanical device 100 can include straight forward lithography,etching, and deposit steps. A material stack of silicon and oxide can beetched from an oxide side. Poly-silicon and oxide can be deposited toform Bragg reflectors with appropriate thicknesses. Mirrors 110, 120forming cavity 200 can be formed in a high index of refraction system(e.g., refractive index of silicon 3.5, refractive index of oxide (1.5))using a quarter wave stack. A mechanical suspension for first mirror 110can be provided by a system of silicon cantilevers.

In one embodiment, cavity 200 can exhibit characteristics that arenon-reciprocal, i.e., cavity 200 can be operative to interact withincident light incident in a first direction differently from light thatis incident in a second direction. In cavity 200, first mirror 110 canbe provided by a movable mirror and second mirror 120 can be astationary mirror. For a light beam incident on cavity 200 in a firstdirection (incident first on the first mirror 110) at the opticalresonance wavelength (frequency), the net momentum imparted per secondon the movable mirror is −((2η−1)−R)I/c (where η is the power build upfactor of the cavity, R is the power reflectivity of the FP cavity, I isthe incident power and c is the speed of light in vacuum, and thenegative sign indicates that the direction of the force is away from thecavity). For a light beam incident on cavity 200 in a second direction(incident first on second mirror 120 which is stationary in the example)the net momentum imparted per second on the movable mirror is−((2η−1)+R)\1c. Hence the differential radiation force for left andright incident beams is 2RIZc producing a non-reciprocal mechanicalresponse from first mirror 110 leading to non-reciprocal opticaltransmittivity (transmission) spectra. There is set forth herein amethod comprising providing an optomechanical device, the optomechanicaldevice being adapted so that forward incident light results in a firstset of radiation forces being imparted to optomechanical device, theoptomechanical device further being adapted so that backward incidentlight results in a second set of radiation forces being imparted to theoptomechanical device, the optomechanical device having a firsttransmittivity band when the first set of forces are imparted to theoptomechanical device, the optomechanical device having a secondtransmittivity band when the second set of forces are imparted to theoptomechanical device; and directing light toward the optomechanicaldevice at a central wavelength matching the first transmittivity band.

A diagram illustrating an optical transmittivity (transmission) spectraof optomechanical device 110 in one embodiment is shown in FIG. 3. It isseen that because of the non-reciprocal mechanical response of cavity200, a transmittance bandwidth of a forward incident light beam incidenton the cavity in a first direction can be differentiated from a backwardincident light beam incident on the cavity in a second direction.

An exemplary practical application for optomechanical device 100 whichexhibits non-reciprocal behavior is shown and described in relation inFIG. 3. In the embodiment of FIG. 3, optomechanical device 100 includesan associated light source 50. Light source 50 can be operative to emitcoherent light at a certain central wavelength. Light source 50 in oneembodiment can be a laser light source. A risk to the operation of lightsource 50 is posed by reflected returned light having the certaincentral wavelength that can be reflected from an object external tolight source and reflected back to light source 50. In the embodiment ofFIG. 3, cavity 200 is operative as an optical isolator to isolatereflected returned light and to prevent returned reflected light frombeing transmitted to light source 50. Referring to the plot of FIG. 4,it is seen that reflected light at the certain central wavelength oflight emitted from light source 50 incident on cavity 200 and within thetransmittivity band of cavity 200 in the forward direction can bereflected or absorbed by cavity 200 rather than transmitted.

In the embodiment of FIG. 4, peak transmittivity in the forwarddirection is approximately 0.1 of the transmittivity (of about 1.0) inthe backward direction. It will be seen that where a forward incidentbeam is in the direction of backward beam 20, the forward incident beamwould have a peak transmittivity of about unity (about 1.0), withbackward incident beam having a transmittivity of about 0.1. As has beendescribed, the sum of forces (net force) incident on mirror 110 in theforward direction will be unequal to the net force incident on mirror110 in the backward direction. Accordingly, it will be seen that the netforce incident on mirror 110 will be unequal in the case that forwardand backward light are simultaneously incident on cavity 200. The casewhere forward and backward light are simultaneously incident on cavity200 occurs where a forward incident light beam is active at the timereflected light is received. Because the net force on mirror 110 in caseof simultaneously incident forward and backward light is not equal tothe net force incident or mirror 110 when only a forward beam isincident on cavity, there will be a shift in the resonance wavelengthband of cavity 200 where reflected light is received by cavity 200 witha forward incident beam simultaneously active. In one embodiment, cavity200 can be configured so that cavity 200 is in resonance on thecondition that forward propagating light only is incident therein butnot in resonance (and not transmitting) in the case of forward andbackward light being simultaneously incident (as in the case ofreflection with a forward incident beam active). The “not transmit”condition herein in one embodiment can be regarded as the condition atwhich transmittivity is below a predetermined low threshold.

Accordingly, cavity 200 can be configured to exhibit non-transmittivecharacteristics when forward and backward light are simultaneouslyincident, and/or when backward light only is incident on cavity 200. Inone embodiment, device 100 can be configured so that light source 50emits pulsed light with continuously switching on and off states,wherein reflection can be expected to be received during the off states.In such embodiment, cavity 200 can be configured to perform an isolationfunction by being configured to exhibit non-transmittive characteristicswhen backward light only is incident thereon. There is set forth hereinan optomechanical device comprising a light source; a first mirror; anda second mirror forming with the first mirror a cavity; wherein thefirst mirror is a movable mirror; wherein the optomechanical device isadapted so that the first mirror is moveable responsively to radiationforce; wherein the light source emits light at a certain centralwavelength, and wherein the optomechanical device is operative so thatlight emitted from the light source incident on the cavity in a forwarddirection results in a first set of radiation forces being imparted onthe first mirror, and wherein the optomechanical device is furtheroperative so that reflected light having the certain central wavelengthincident on the cavity in a backward direction simultaneously with lightfrom the light source being incident on the cavity in the forwarddirection results in a second set of radiation forces being imparted onthe first mirror, wherein a sum of the first set of radiation forces,and a sum of the second set of radiation forces are not equal so thatthere is defined for the cavity a first resonance wavelength band forlight incident on the cavity in the forward direction and a secondresonance wavelength band for light incident on the cavity in thebackward direction simultaneously with light from the light source beingincident on the cavity in the forward direction, wherein the certaincentral wavelength is matched to the first resonance wavelength band butnot matched to the second resonance wavelength band so that thereflected light at the certain central wavelength is not transmitted bythe cavity.

By movement of a distance spacing of first mirror 110 relative to secondmirror 120, a resonance band of cavity 200 can be shifted. A plotindicating a peak transmission wavelength as a function of distancespacing is shown at FIG. 4. In the development of optomechanical device100 it was determined that maintaining a distance spacing of firstmirror 110, which can be moveable at a certain spacing distance may bechallenging in view of practical imperfections of a light source, firstmirror 110 and the mechanical suspension for arranging first mirror 110,and further in view of characteristics of the various elements of cavity200 under resonance.

Accordingly, in view of an expected instability of moveable mirror 110,an optomechanical device as set forth herein can in include a mechanicalstop 70 for stopping movement of the mirror in one direction in responseto an imparted radiation force. Features of a mechanical stop in oneembodiment are as follows. In one aspect, a mechanical stop 70 can havea spring constant sufficient so that movement of mirror 110 isrestricted to provide stable positioning of mirror 110. In anotheraspect, a mechanical stop 70 can be provided so as to be resistant toadhering with externally disposed objects such as mirror 110. Forexample, stop 70 can be provided to have a polymer coating, or can befabricated using special fabrication methods. Further, a mechanical stop70 can be configured to provide a damped response, e.g., with minimal orwithout oscillations. Still further, stop 70 should be arranged to theyare not to affect an optical function of a cavity.

A mechanical stop 70 can be provided for limiting a maximum distance atwhich a first and second mirror 110, 120 can be spaced.

In the embodiment of FIG. 5, optomechanical device 100 can be providedto limit a power of light transmitted by a light source. In theembodiment of FIG. 5, light source 50 can be disposed to project lightonto cavity 200, and cavity 200 can be arranged to limit lighttransmitted at higher powers. Optomechanical device 100 in theembodiment of FIG. 5 can be regarded as a power limiter.

Cavity 200 can be provided so that in an initial state cavity 200 has aresonance wavelength band that is matched to the emission centralwavelength. However, cavity 200 can also be adapted so that on receiptby cavity 200 of incident light, mirror 110 can move to shift aresonance wavelength band of cavity 200. It will be seen that the amountof the shift can be a function of the power of the incident light. Aplot showing cavity transmittivity as a function of input light energyis shown in FIG. 6. It is seen that as the power of the emitted lightincreases moving mirror 110 can move to shift a resonance wavelength ofcavity 200. At some point in the shift a resonance band of the cavity200 can be expected to become mismatched relative to the centralwavelength of the incident light incident on cavity 200. At such pointcavity 200 will not transmit. As indicated, the “not transmit” conditionherein in one embodiment can be regarded as the condition at which atransmittivity is below predetermined low threshold. Referring to thepower limiter example of FIG. 5, it can be seen that when sufficientlyhigh power light is incident on cavity 200, a resonance wavelength bandof cavity 200 can shift between a first resonance wavelength bandmatched to a certain central wavelength to a second resonance wavelengthband not matched to a certain central wavelength. There is set forthherein an optomechanical device comprising a first mirror; and a secondmirror forming with the first mirror a cavity; wherein the first mirroris a movable mirror; wherein the optomechanical device is adapted sothat the first mirror is moveable responsively to radiation force;wherein during an initial state a resonance wavelength band of thecavity is matched to a certain central wavelength so that the cavity iscapable of transmitting light emitted from a light source that emitslight at the certain central wavelength, and wherein the optomechanicaldevice is adapted so that a set of radiation forces on the first mirrorattributable to emission of light at the certain central wavelength withsufficient power results in a resonance wavelength band of the cavityshifting from a wavelength band at which the resonance wavelength bandof the cavity is matched to the certain central wavelength to awavelength band at which the resonance wavelength band is not matched tothe certain central wavelength.

A summary of states of the optomechanical device of FIG. 5 is summarizedin Table A below.

TABLE A Table A Power of Emitted Mirror State Light Spacing Resonance ofCavity Result Initial No Power d₁ Not Matched to No Initial CentralWavelength Beam of Incident Beam Low Power Low Power d₁ Matched toCentral Beam is Wavelength of Transmitted Incident Beam High Power HighPower d₂ Not Matched to Beam is Not Central Wavelength Transmitted ofIncident Beam

In the embodiment of FIG. 7, optomechanical device 100 can be provide torestrict transmittance of low power incident light, and selectivelytransmit light at higher powers. In the embodiment of FIG. 7, lightsource 50 is disposed to project light onto cavity 200, and cavity 200is arranged to limit light transmitted at lower powers. Referring toFIG. 7, light source 50 can emit light at a certain central wavelengthand can be a variable power light source variable to emit light havingwattage of between OW and NW. Cavity 200 can be provided so that in aninitial state cavity 200 has a resonance wavelength band that matchesthe emission central wavelength. However, cavity 200 can also be adaptedso that on receipt of incident light, mirror 110 can move to shift aresonance wavelength band of cavity 200. It will be seen that the amountof the shift can be a function of the power of the incident light. Aplot showing cavity transmittivity as a function of input light energyis shown in FIG. 8. It is seen that as the power of the emitted lightincreases moving mirror 110 can move to shift a resonance wavelength ofcavity 200. At some point in the shift, a resonance band of the cavity200 can be expected to become matched relative to the central wavelengthof the incident light. At such point cavity 200 is capable oftransmitting. In the embodiment of FIG. 7, optomechanical device 100 caninclude stop 70 for aiding the stabilizing of mirror 110 at a certainposition to yield a stable resonance frequency band for cavity 200. Anoptomechanical device 100 as set forth in FIG. 7 can be regarded as asaturable absorber. A saturable absorber as described with reference toFIG. 7 can be utilized in combination with a laser light source for modelocking. Referring to the embodiment of FIG. 7, it can be seen thatwhere sufficiently high power light is incident on cavity 200, aresonant wavelength band of cavity 200 can shift between a firstresonant wavelength band not matched to a central wavelength of emittedlight to a second resonant wavelength band matched to a centralwavelength of emitted light. There is set forth herein an optomechanicaldevice comprising a first mirror; and a second mirror forming with thefirst mirror a cavity; wherein the first mirror is a movable mirror;wherein the optomechanical device is adapted so that the first mirror ismoveable responsively to radiation force; wherein during an initialstate a resonance wavelength band of the cavity is not matched to acertain central wavelength so that in an initial state the cavity isrestricted from transmitting light emitted from a light source at thecertain central wavelength, and wherein the optomechanical device isadapted so that a set of radiation forces on the first mirrorattributable to emission of light at the certain central wavelength withsufficient power results in a resonance wavelength band of the cavityshifting from a wavelength band at which the resonance wavelength bandof the cavity is not matched to the certain central wavelength to awavelength band at which the resonance wavelength band of the cavity ismatched to the certain central wavelength.

Table B summarizes possible states of the optomechanical device of FIG.7.

TABLE B Table B Power of Emitted Mirror State Light Spacing Resonance ofCavity Result Initial No Power d₁ Matched to Central No Initial BeamWavelength of Incident Beam Low Low Power d₁ Not Matched to Beam is NotPower Central Wavelength Transmitted of Incident Beam High High Power d₂Matched to Central Beam is Power Wavelength of Transmitted Incident Beam

In the embodiment of FIG. 9, optomechanical device 100 is operative toprovide a power band pass function; that is, transmit light emittedwithin a predetermined power band for a particular central wavelength ofemission, but not transmit light emitted at power either less than orgreater than the power pass band. A transmittivity plot for the deviceof FIG. 9 is shown in FIG. 10. In an initial state, cavity 200 is in astate where it does not transmit light incident at the centralwavelength of the incident light. At intermediate power, a resonanceband can become matched with the central wavelength of the incidentlight and cavity 200 can transmit emitted light emitted from lightsource 50. At higher power, a distance between mirror 110, 120 canchange again to change a resonance band of cavity 200 again so thatcavity 200 again becomes mismatched with the resonance band of theincident light so that cavity 200 again does not transmit. Referring tothe example of FIG. 9, it can be seen that when appropriately high powerlight is incident on the cavity of FIG. 9 at a certain centralwavelength, a resonance wavelength band can shift between a firstresonance wavelength band at which the resonance wavelength band is notmatched to a central wavelength, a second resonance wavelength band atwhich the resonance wavelength band is matched to a central wavelength,and a third resonance wavelength band at which the resonance wavelengthband is not matched to a central wavelength. There is set forth hereinan optomechanical device comprising a first mirror; and a second mirrorforming with the first mirror a cavity; wherein the first mirror is amovable mirror; wherein the optomechanical device is adapted so thatradiation force on the first mirror attributable to emission of light ofa certain central wavelength with sufficient power results in aresonance wavelength band of the cavity shifting between a first statein which a resonance wavelength band of the cavity includes a set ofwavelengths shorter than a wavelength band matched to a certain centralwavelength, a second state in which a resonance wavelength band of theemitted light is matched to a the certain central wavelength, and thethird state in which the resonance wavelength band of the cavityincludes a set of wavelengths longer than a wavelength band matched tothe certain central wavelength. A summary of states of the embodiment ofFIG. 9 is summarized in Table C.

TABLE C Table C Power of Emitted Mirror Resonance of State Light SpacingCavity Result Initial No Power d₁ Not Matched to No Initial Beam CentralWavelength of Incident Beam Low Power Low Power d₁ Not Matched to Beamis Not Central Transmitted Wavelength of Incident Beam IntermediateIntermediate d₂ Matched to Beam is Power Power Central TransmittedWavelength of Incident Beam High Power High Power d₃ Not Matched to Beamis Not Central Transmitted Wavelength of Incident Beam

For scaling up optical systems in which a cavity 200 as described areincorporated, cavity 200 can be incorporated into arrays of cavities. InFIG. 11, there is shown an array 600 of cavities 200 formed in a onedimensional array of cavities 200 in which cavities 200 are arranged inseries so that axes of adjacent ones of cavities 200 are aligned. Sucharrangement can be useful for achieving complex transmittivitycharacteristics for optomechanical device 100. In FIG. 12, there isshown an array of cavities formed as a two dimensional array of cavitieswith a plurality of cavities 200 extending horizontally and a pluralityof cavities extending vertically. One dimensional array 600 (FIG. 11)and two dimension array 700 (FIG. 12) can have the cross-section of anoptical cavity as shown in FIG. 2 and can be formed by scaling up afabrication process for fabricating the cavity as described withreference to FIG. 2.

In another aspect as is illustrated in FIG. 13, a plurality of arrays700 can be configured in a series (stacked) configuration (FIG. 13illustrates the case of plurality of stacked two dimensional arrays700). In a stacked configuration, axes of adjacent ones of arrays 700can be aligned. Stacking of arrays can increase a transmittivitywavelength band of an optical system.

Regarding the low power pass (power limiter) embodiment of FIGS. 4 and5, such an optomechanical device among numerous other uses can beutilized for providing eye protection to persons who may be exposed tootherwise harmful light beams. The optomechanical device of FIGS. 4 and5 can be configured to provide power sensitive transmittivity andreflectivity with respect to incident light having the centralwavelength for which the device is to provide protection. For example,where optomechanical device 100 is to provide protection relative to agreen emitting light source, optomechanical device 100 can be configuredto provide appropriate power sensitive transmittivity at about theemitted central wavelength of the light source within the green band.

In FIG. 14, there is shown optomechanical device adapted for providingeye protection. Optomechanical device 100 as shown in the embodiment ofFIG. 14 can incorporate an array 700 to provide eye protection over alarge two dimensional area of emitted light for which eye protection isto be provided. In the embodiment of FIG. 14, optomechanical device 100can be configured as an eyewear apparatus. In the embodiment of FIG. 14,optomechanical device 100 can include eyewear apparatus frame 710 thatsupports array 700, and which accordingly supports a plurality ofcavities 200. Frame 710, in one embodiment, can incorporate a stackedarray as shown in FIG. 13. Shown in the form of protective eyeglasses,an eyewear apparatus incorporating cavity 200 can also include, e.g., avisor, goggles, or a shield each having an associated eyewear apparatusframe (but of different configuration than that shown in FIG. 14) whichcan support a cavity 200.

Another embodiment of optomechanical device 100 is described withreference to FIGS. 15-16. In the embodiment of FIGS. 15-16, cavity 200is provided as an in-plane optomechanical device having an in-planedevice structure. In the embodiment of FIGS. 15-16, first mirror 110 andsecond mirror 120 can be provided by drop rings. First mirror 110 andsecond mirror 120 as shown in FIGS. 15-16 are shown as being provided ina common plane. First mirror 110 can be made moveable by appropriatesizing of first mirror 110 as seen in FIGS. 15-16. In another aspect,optomechanical device 100 can include first waveguide 180 opticallycoupled to a first set of lateral edges of first mirror 110 and secondmirror 120, and an oppositely disposed second waveguide 190 can beoptically coupled to a second set of lateral edges of first mirror 110and second mirror 120. Optomechanical device 100 can also include stop70 for stopping of moveable mirror 110. Mirrors 110, 120 can includetransmittivity characteristics such that mirrors 110, 120 are reflectivewith respect to a certain band of incident light and transmittive withrespect to light outside the certain band. When forward light (movingleft to right in FIGS. 15-16) is input into cavity 200 through firstwaveguide 180 with a central wavelength matched the reflective bands offirst mirror 110 and second mirror 120, light can be reflected betweenfirst mirror 110 and second mirror 120 resulting in radiation buildupwithin cavity 200. Like the embodiments of FIGS. 1, 3, 5, 7, and 9herein forward propagating light incident on cavity 200 can result in adifferent net force on mirror 110 than backward light yieldingnon-reciprocal behavior of cavity 200 and optomechanical device 100.

An excerpt is presented herein from U.S. Provisional Patent ApplicationNo. 61/153,913 with minor formatting changes and with reference numeralschanged to avoid duplication.

[Excerpt taken from U.S. Provisional Patent Application No. 61/153,913].

There are described non reciprocal optomechanical devices which define anew class of optical functionalities in micro-photonics such asisolators, circulators, in-line reflection sensors, saturable absorbers,and power limiters. There is also described an optomechanical systemwhere dominant light-matter interaction takes place via linear momentumexchange between light and the mechanical structure leading to anon-reciprocal behavior. There is further described a device thatexhibits different optical behavior for a probe beam for forward andbackward propagating pump beams. In one described embodiment,non-reciprocal behavior can be observed in the limit of a strong probe.There are further described planar and non-planar optomechanical devicesthat can exhibit this behavior in a micro photonic platform. A class ofdevices is described that can enable new functionalities for integratedoptical systems.

Details of the above described embodiments and additional embodimentsare set forth in the manuscript entitled “Optical Non-Reciprocity inOptomechanical Structures” which is attached hereto as Appendix A andwhich forms part of the present disclosure and in the manuscriptentitled “Optomechanical Non-Reciprocal Device” which is attached heretoas Appendix B and which also forms part of the present disclosure.

[The following section is excerpted from Appendix A of U.S. ProvisionalPatent Application No. 61/153,913]

Breaking the reciprocity of light on-chip can lead to an important newclass of optical devices such as isolators, which are critical for thedevelopment of photonic systems. Traditional methods for creatingnon-reciprocal devices rely on magneto-optic media, optically-activemedia or photovoltaic electro-optic crystals (P. S. Pershan,“Magneto-Optical Effects,”/. Appl. Phys. 38, 1482 (1967); J. Fujita, M.Levy, R. M. Osgood, Jr., L. Wilkens, and H. Dotsch, “Waveguide opticalisolator based on Mach-Zehnder interferometer”, Appl. Phys. Lett. 76,2158 (2000); D. C. Jones, G. Cook, “Nonreciprocal transmission throughphotorefractive crystals in the transient regime using reflectiongeometry,” Opt. Commun. 180 391-402 2000; R. J. Potton, “Reciprocity inoptics,” Rep. Prog. Phys. 67, 717-754 (2004)). Non-reciprocal behaviourhas also been studied in time varying media (D. M. Shupe, “Thermallyinduced non-reciprocity in the fiber-optic interferometer,” Appl. Opt.19, 654-655 (1980); Z, Yu, and S. Fan, “Complete optical isolationcreated by indirect interband photonic transitions,” Nature Photonics2009. Advanced online publication doi:10.1038/nphoton.2008.273),bi-anisotropic media (Bianisotropic media are the most general linearcomplex media where the constitutive relationships are defined by 4second rank tensors as

$\begin{matrix}{{D = {ɛ_{0}\left( {{ɛ \cdot E} + {\eta_{0}{\xi \cdot H}}} \right)}},{B = {\frac{1}{c_{0}}\left( {{\zeta \cdot E} + {\eta_{0}{\mu \cdot H}}} \right)}}} & \left\lbrack {{Eq}.\mspace{14mu} 3} \right\rbrack\end{matrix}$where D, E, B and H are the macroscopic electromagnetic fields; J. A.Kong, “Theorems of bianisotropic media,” Proc. IEEE, Vol. 60, No. 9 Sep.1972)) (such as magneto-electric media), and relativistic moving media(A. Sommerfeld, Electrodynamics. New York: Academic Press, 1952 Page280). However, the development of non-reciprocal devices for amicro-photonic platform remains a challenge (Z, Yu, and S. Fan,“Complete optical isolation created by indirect interband photonictransitions,” Nature Photonics 2009. Advanced online publicationdoi:10.1038/nphoton.2008.273). Hence, it is of great interest to pursuealternative mechanisms to break the reciprocity of light on amicro-scale platform. Here, we show non-reciprocity by exploiting afundamental difference between forward and back moving light: itsmomentum. Recent work in optomechanics (T. J. Kippenberg and K. J.Vahala, “Cavity Opto-Mechanics,” Opt. Express 15, 17172-17205 (2007),enabled by advances in optical micro cavities (K. J. Vahala, “Opticalmicrocavities,” Nature 424(6950), 839-846 (2003) andnano-electro-mechanical systems (H. G. Craighead, “Nanoelectromechanicalsystems,” Science 290(5496), 1532-1535 (2000), has shown tremendouspotential for a new class of micro-scale devices (T. Cannon, H.Rokhsari, L. Yang, T. J. Kippenberg, K. J. Vahala, Temporal Behavior ofRadiation-Pressure-Induced Vibrations of an Optical Microcavity PhononMode, Phys. Rev. Lett. 94, 223902 (2005); M. L. Povinelli, J. M.Johnson, M. Loncar, M. Ibanescu, E. J. Smythe, F. Capasso, and J. D.Joannopoulos, “High-Q enhancement of attractive and repulsive opticalforces between coupled whispering-gallery-mode resonators,” OpticsExpress 13(20), 8286-8295 (2005); M. Eichenfeld, C. Michael, R. Perahia,and O. Painter, “Actuation of Micro-Optomechanical Systems ViaCavity-Enhanced Optical Dipole Forces,” Nature Photonics 1(7), 416(2007); P. T. Rakich, M. A. Popovic, M. SoIj acic, E. P. Ippen.“Trapping, corralling and spectral bonding of optical resonances throughoptically induced potentials”, Nature Photonics 1 (11), 2007, p. 658;Wiederhecker, G. S., Chen, L., Gondarenko, A. and Lipson, M.,Controlling photonic structures using optical forces, Arxiv 0904.0794v1)and novel physical phenomena such as optomechanical cooling (K. C.Schwab and M. L. Roukes, “Putting mechanics into quantum mechanics,”Physics Today 58(7), 36-42 (2005); V. B. Braginsky and S. P. Vyatchanin,“Low quantum noise tranquilizer for Fabry-Perot interferometer,” PhysicsLetters A 293(5-6), 228-234 (2002); M. D. LaHaye, O. Buu, B. Camarota,and K. C. Schwab, “Approaching the quantum limit of a nanomechanicalresonator,” Science 304(5667), 74-77 (2004); A. Naik, O. Buu, M. D.LaHaye, A. D. Armour, A. A. Clerk, M. P. Blencowe, and K. C. Schwab,“Cooling a nanomechanical resonator with quantum back-action,” Nature443(7108), 193-196 (2006); O. Arcizet, P. F. Cohadon, T. Briant, M.Pinard, and A. Heidmann, “Radiation-pressure cooling and optomechanicalinstability of a micromirror,” Nature 444(7115), 71-74 (2006); M. Li, W.H. P. Pernice, C. Xiong, T. Baehr-Jones, M. Hochberg, H. X. Tang, Nature456, 480-484 (2008)). In this paper, we show that when the dominantlight-matter interaction takes place via momentum exchange,optomechanical devices can exhibit non-reciprocal behaviour; since theiroptical spectral characteristics are strongly dependent upon thedirection of the incidence of light. We propose a silicon basedmicro-optomechanical device that exhibits a non-reciprocal behaviourwith a contrast ratio>20 dB.

An example of an optomechanical structure which interacts with lightthrough linear momentum exchange consists of an in-line Fabry Perot (FP)cavity with one movable mirror and one fixed mirror (FIG. 17). Theemergence of non-reciprocity in such as system can be understood asfollows (see FIG. 17, left diagram): For a left-incident beam at theoptical resonance frequency, the net momentum imparted per second on themovable mirror is −((2//−I)−R)I/c (where η is the power build up factorof the cavity, R is the power reflectivity of the FP cavity, / is theincident power and c the speed of light in vacuum, and the negative signindicates that the direction of the force is away from the cavity). Onthe other hand, for a right-incident beam the net momentum imparted persecond on the movable mirror is −((2η−1)+R)Vc. Hence the differentialradiation force for left and right incident beams is 2RI/c producing anon-reciprocal mechanical response from the mirror leading tonon-reciprocal optical transmission spectra.

To illustrate the non-reciprocal behavior in a realisticmicro-optomechanical device we describe a representative device whichcan be fabricated in a silicon material system. The device (FIG. 18)consists of a quasi-ID standing wave cavity formed by two quarter waveBragg reflectors with one of the mirrors suspended via micro-cantilevers(B. Ilic, H. G. Craighead, S. Krylov, W. Senaratne, C. Ober, P. Neuzil,“Attogram Detection Using Nanoelectromechanical Oscillators”, Journal ofApplied Physics, 95, 3694-3703 (2004)). The mirrors forming the cavityare fabricated in a high index contrast system (the refractive indicesof Si and Siθ₂ are approximately 3.5 and 1.5 respectively). Springconstants spanning several orders of magnitude can be achieved(typically from 10″ Nm^(″1) to 1 Nm^(″1) [24]), by varying thematerials, geometry and the arrangement of the cantilevers. We model themovable mirror as a vertical translation plate supported by four beams.Using COMSOL (M. Bao, H. Yang, “Squeeze film air damping in MEMS”,Sensors and Actuators A 136 (2007) 3-27) software package we compute themechanical response of the structure by including material propertiesand boundary conditions into a Finite Element Method (FEM) based solver.No angular displacement is allowed because the beams are connected tothe mirror which remains parallel to the substrate under nominal platemovements. The spring constant associated with four fixed beams is givenby 4Ewt³/l³ where E is the young's modulus and w, t, and/are the width,thickness, and length of the silicon beams respectively(www.comsol.com). In a given material system, the cubic dependence ofthe spring constant on the aspect ratio (t/l) allows for a wide range ofspring constants for this beam geometry. We consider a 10×10 μm² mirrorsuspended using micro-cantilevers of thickness 110.5 nm {˜λJAn_(si)where λ_(c) is 1550.5 nm and n_(si) (3.5) the refractive index ofsilicon), 10 μm length, and 100 nm width. The mass of the mirror is165.26 pg. The spring constant for the chosen dimensions is 0.06Nm^(″1). Using the FEM software we calculate the mechanical displacementof the movable mirror for −666 pN (2I/c) applied force corresponding toa net radiation force from a 100 mW beam reflected perfectly from themirror (see FIG. 18) to be on the order of 10 nm. The bandwidth of theoptical cavity formed by the mirrors is primarily determined by thereflectivity of the mirrors. We show the optical transmissioncharacteristics of the device in FIG. 21. We consider quarter wavestacks on either side formed by alternating layers of Si and Siθ₂ with 2layers of deposited silicon and three layers of deposited oxide. Themirrors form an air filled cavity of length ˜5(M_(c)/2. The qualityfactor of the cavity [Q=X₀ZAX) is −5200 centred at ˜Λ._(c)=1550.5 nm.The mirror layers have thicknesses of 21λ_(mirror1)/4 n_(si),21λ_(mirror2)/4 n_(si).

Non-reciprocal behavior in the proposed structure emerges due to theasymmetry of the radiation pressure on the movable mirror for forwardand backward incident light. We model the cantilever dynamics by adriven second order differential system with a non-linear drivingfunction

$\begin{matrix}{{\frac{\mathbb{d}^{2}x}{\mathbb{d}t^{2}} + {\frac{b}{m_{eff}}\frac{\mathbb{d}x}{\mathbb{d}t}} + {\frac{K}{m_{eff}}x}} = \frac{F_{RP}\left( {\lambda,x,t} \right)}{m_{eff}}} & \left\lbrack {{Eq}.\mspace{14mu} 4} \right\rbrack\end{matrix}$where radiation force on die movable mirror is

$\begin{matrix}{{F_{RP}\left( {\lambda,x,t} \right)} = \left\lbrack \begin{matrix}{{- \left( {\left( {{2\eta} - 1} \right) - {R\left( {\lambda,x,t} \right)}} \right)}*I\text{/}c} & {{for}\mspace{14mu}{forward}\mspace{14mu}{incidence}} \\{{- \left( {{2\eta} - 1 + {R\left( {\lambda,x,t} \right)}} \right)}*I\text{/}c} & {{for}\mspace{14mu}{backward}\mspace{14mu}{incidence}}\end{matrix} \right.} & (2)\end{matrix}$where I is the power of the incident beam η, R are the intensity buildup factor, and reflectivity of the cavity for wavelength λ and movablemirror position x. The position dependent reflectivity R(λ, x, t) isgiven as a function of displacement x as,

$\begin{matrix}{{R\left( {\lambda,x,t} \right)} = {1 - \left\lbrack {\left( \frac{\left| {t_{1}t_{2}} \right|}{\left. {1 -} \middle| {r_{1}r_{2}} \right|} \right)^{2}\frac{1}{1 + {4\left( \frac{\sqrt{\left| {r_{1}r_{2}} \right|}}{\left. {1 -} \middle| {r_{1}r_{2}} \right|} \right)^{2}\sin^{2}\mspace{14mu}{\varphi(x)}}}} \right\rbrack^{1\text{/}2}}} & \left\lbrack {{Eq}.\mspace{14mu} 5} \right\rbrack\end{matrix}$where φ(x) is the phase shift per round trip inside the cavity:

$\frac{1}{2}{{Arg}\left\lbrack {r_{1}r_{2}{\mathbb{e}}^{{\mathbb{i}}\frac{2\pi}{\lambda}{({l - x})}}} \right\rbrack}$and r₁, r_(2 &) t₁, t₂ are the mirror reflectivties andtrasnmittivities; / is the steady state cavity length. We assume a massof 165.26 pg, spring constant of 0.06 Nm^(″1) (corresponding to a 10×10μm² Bragg mirror, see FIGS. 18-21) and a net damping parameter of10^(″6) kgs^(″1). The damping mechanisms may include mass damping,stiffness damping, acoustic leakage at the anchors and thin fluidsqueezing (M. Bao, H. Yang, “Squeeze film air damping in MEMS”, Sensorsand Actuators A 136 (2007) 3-27). The coupled optomechanical response iscalculated at each time step (1 ns˜τ_(mechamca)i/1600) by updating boththe optical and mechanical state of the cavity. We also note that thephoton life time (τ_(PhO)tO_(n)=A.Q/2πc˜4.1 ps) is much smaller than themechanical rise time (τ_(mech)a_(m)cai=b/m˜\6 ns), which allows for thecalculation of the optomechanical response iteratively. We neglect thequantum Langevin noise in calculating the optomechanical response. Thetransmission spectral characteristics exhibit the classical behaviour ofoptical bi-stable systems. The transmission spectra of the device forforward and backward incident light are shown in FIGS. 22-23. One cansee the formation of a non-reciprocal transmission window at 1551.2 nmwith a bandwidth of 0.25 nm and a forward to backward incident lightextinction ratio of >16 dB. The transition time for back ward to forwardincidence (and vice versa) is on the order of (≈(½Q_(m))*(√{square rootover (K/m_(eff))}), where Q_(1n) is the mechanical quality factor) givenby mechanical design of the movable mirror.

The insertion loss through the device can be minimized by providing amechanical stop for the movable mirror. To obtain a unity peaktransmission, the FP cavity needs to be perfectly on resonance with theincoming light. However when the cavity is perfectly on resonance, theradiation force on the mirror passes through a maximum leading toinstability (T. Carmon, H. Rokhsari, L. Yang, T. J. Kippenberg, K. J.Vahala, Temporal Behavior of Radiation-Pressure-Induced Vibrations of anOptical Microcavity Phonon Mode, Phys. Rev. Lett. 94, 223902 (2005)). Amechanical stop allows for peak resonance build up while producing a nonreciprocal response. We describe a non-reciprocal optomechanical deviceto achieve low insertion loss (<0.1 dB), high forward to backwardincidence extinction ratio (>20 dB). In FIG. 24, we show thetransmission spectra for forward and back ward incident light of 100 mWpower when the mirror is constrained to −30 nm displacement. One can seethe formation of a non-reciprocal spectrum with a 0.25 nm bandwidth anda forward to back ward light extinction ratio>20 dB. The insertion lossfor the backward light is now <0.1 dB. The bandwidth of thenon-reciprocal spectrum can be controlled by choosing the appropriatemirror reflectivity. We note that an important consideration for amechanical stop is the affect of stiction force for mechanical objectsin close proximity. However earlier works have successfully demonstratedvarious methods to overcomes this problem (Maboudian, R., W. R. Ashurstand C. Carraro, Tribological challenges in micromechanical systems. 12(2002) 95; R. Maboudian and R. T. Howe, Stiction reduction processes forsurface micromachines. Tribol. Lett. 3 (1997), p. 215).

The thermal equipartition noise imposes a minimum power condition forobserving the non-reciprocal behavior. We estimate the optical powerrequired for the radiation force displacement to exceed the mean squaredisplacement of the mirror for a given spring constant. The minimumoptical power required to overcome the thermal position noise is givenby I_(min)=cKΔx, where Δx_(min)=√{square root over (kT/K)}, k theBoltzmann constant, K the spring constant, and T=300 K ambienttemperature. Following the fluctuation dissipation theorem, thisanalysis takes into account the Langevin noise (Kubo, R. Thefluctuation-dissipation theorem. Rep. Prog. Phys. 29, 255-284 (1966)).One can see that the net optical power contributing to thenon-reciprocal behaviour should be in the range of 10's of mW toovercome the thermal equipartition noise. The optical power I_(min) canbe lowered by lowering the spring constant. Even though thermalnon-linearity has traditionally been an important constraint tomicro-photonic devices (Cannon, T., Yang, L. & Vahala, KJ. “Dynamicalthermal behaviour and thermal selfstability of microcavities”. OpticsExpress 12, 4742 (2004)), we note that the effect of thermalnon-linearity will only contribute equally to both directions ofincidence. The general principles described here for creating deviceswith non-reciprocal transmission spectra can be extended to in-planegeometry by employing suspended resonators (L. Martinez and M. Lipson,“High confinement suspended micro-ring resonators insilicon-on-insulator,” Opt. Express 14, 6259-6263 (2006)) as frequencyselective reflectors (S. Manipatruni, P. Dong, Q. Xu, and M. Lipson,“Tunable superluminal propagation on a silicon microchip,” Opt. Lett.33, 2928-2930 (2008). This class of devices with non-reciprocal spectracan enable new functionalities for integrated optical systems.

[End of Section Excerpted as Appendix A of U.S. Provisional PatentApplication No. 61/153,913]

[The Following Section Is Excerpted From Appendix B of U.S. ProvisionalPatent Application No. 61/153,913]

Recent work in optomechanics (T. J. Kippenberg and K. J. Vahala, “CavityOpto-Mechanics,” Opt. Express 15, 17172-17205 (2007)), enabled byadvances in optical micro cavities (K. J. Vahala, “Opticalmicrocavities,” Nature 424(6950), 839-846 (2003)) andnano-electromechanical systems (H. G. Craighead, “Nanoelectromechanicalsystems,” Science 290(5496), 1532-1535 (2000)), has shown tremendouspotential for new classes of micro scale devices (T. J. Kippenberg, H.Rokhsari, T. Carmon, A. Scherer, and K. J. Vahala, “Analysis ofRadiation-Pressure Induced Mechanical Oscillation of an OpticalMicrocavity,” Physical Review Letters 95, 033,901 (2005), M.Hossein-Zadeh and K. J. Vahala, “Photonic RF Down-Converter Based onOptomechanical Oscillation,” Photonics Technology Letters, IEEE, 20,Issue 4, Page(s): 234-236 (2008), M. L. Povinelli, J. M. Johnson, M.Loncar, M. Ibanescu, E. J. Smythe, F. Capasso, and J. D. Joannopoulos,“High-Q enhancement of attractive and repulsive optical forces betweencoupled whispering-gallery-mode resonators,” Optics Express 13(20),8286-8295 (2005), M. Eichenfeld, C. Michael, R. Perahia, and O. Painter,“Actuation of Micro-Optomechanical Systems Via Cavity-Enhanced OpticalDipole Forces,” Nature Photonics 1(7), 416 (2007), O. Arcizet, P. F.Cohadon, T. Briant, M. Pinard, A. Heidmann, J. M. Mackowski, C. Michel,L. Pinard, O. Francais, and L. Rousseau, “High-sensitivity opticalmonitoring of a micromechanical resonator with a quantum limitedoptomechanical sensor,” Physical Review Letters 97(13), 133,601 (2006),P. T. Rakich, M. A. Popovic, M. Soljacic, E. P. Ippen. “Trapping,corralling and spectral bonding of optical resonances through opticallyinduced potentials”, Nature Photonics 1 (11), 2007, p. 658) andphenomena K. C. Schwab and M. L. Roukes, “Putting mechanics into quantummechanics,” Physics Today 58(7), 36-42 (2005)). In this paper, we showthat, when dominant light matter interaction takes place via linearmomentum exchange, it can lead to a non reciprocal behavior where deviceoptical spectral characteristics are modified strongly depending up onthe direction of incidence of light.

Breaking the reciprocity of light can lead to a new class of on-chipoptical devices such as optical isolators and circulators withfunctionalities complementary to reciprocal optical devices such asmodulators, filters, and switches. Traditional methods for nonreciprocal devices rely on magneto-optic media, optically active media,or photovoltaic electrooptic crystals. (P. S. Pershan, “Magneto-OpticalEffects,” J. Appl. Phys. 38, 1482 (1967), J. Fujita, M. Levy, R. M.Osgood, Jr., L. Wilkens, and H. Dotsch, “Waveguide optical isolatorbased on Mach-Zehnder interferometer,” Appl. Phys. Lett. 76, 2158(2000), and D. C. Jones, G. Cook, “Nonreciprocal transmission throughphotorefractive crystals in the transient regime using reflectiongeometry,” Opt. Commun. 180 391-402 2000).

All these materials are hard to integrate on a CMOS compatiblemicro-scale platform which has emerged as a strong candidate for microphotonics. Hence, it is of great interest to pursue alternativemechanisms to break the reciprocity of light on a micro scale platform.

Devices described herein can enable non reciprocal effects (i.e., leftand right moving light see different optical effects from an opticalsystem) on an integrated photonics chip. Devices described herein alsocan provide different optical response for forward (left) and backward(right) propagating optical signals. Devices described herein also cansense presence of a strong optical beam forward or backward and producesdistinguishable responses. Devices described herein also can act as anoptical isolator for strong optical signals. Devices described hereinalso can operate without the use of magneto-optic media, opticallyactive media, or photovoltaic electrooptic crystals. Devices describedherein also can be operated as a saturable absorber or a saturable powerlimiter. Devices described herein also can be operated as a saturableabsorber for use in pulses laser systems. Devices described herein alsocan be used as a safety measure to block intense light for sensitiveoptical systems. Devices described herein also can be fabricated in asilicon CMOS fabrication facility. The proposed device can be used as alight controlled light switch.

A fundamental difference between forward and backward propagating lightis the direction of linear momentum carried by the electromagneticfield. Hence if we can design an optomechanical structure which taps thelinear momentum to reconfigure the optical device, we will be able todifferentiate forward and backward propagating light, thus creating nonreciprocal transmission spectra. We show that the proposed device canachieve this functionality. We also propose planar and non-planaroptomechanical devices which can exhibit this behavior in a microphotonic platform.

In FIG. 26 there is shown an optomechanical structure underconsideration. There is shown Fabry-Perot (FP) cavity with one of themirrors movable and the other fixed to the substrate. The left mirror isreflecting for the pump and probe. The right mirror is reflecting onlyfor the probe.

Here we introduce a general structure for creating a direction sensitivetransmission spectrum using optomechanical structures. The proposedstructure is an in line Fabry Perot (FP) cavity with one movable mirrorand one fixed mirror (FIG. 26, top diagram). The pump signal isreflected only at the movable mirror while the probe signal is reflectedboth at the movable and the fixed mirror. The direction sensitivetransmission spectrum is realized as follows: a) For left incident light(FIG. 26, middle diagram, when the pump is incident from the left of theFP cavity, the reflection of the incident beam produces a net momentumchange of the photons to the left producing radiation pressure to theright. The cavity optical path is reduced leading to a blue shiftedtransmission spectrum, b) For right incident light (FIG. 26, bottomdiagram), when the pump is incident from the right of the FP cavity, theincident beam interacts only with the movable mirror (by appropriatedesign of the fixed mirror) produces a net momentum change of thephotons to the right producing radiation pressure to the left. Thecavity optical path is increased leading to a red shifted transmissionspectrum. In the limiting case of the probe becoming strong, the leftand right incident conditions still produce different momenta on themovable mirror leading to non reciprocal transmission spectra.

In FIG. 27, there is shown proposed optomechanical device for nonreciprocal transmissions. As shown in FIG. 27, quarter wave Braggreflectors are formed at either ends of an Siθ₂ cavity. The structure isfabricated by attaching two SOI wafers. Bragg reflectors are designedsuch that both the reflectors are reflective for the probe signal. Onlythe movable mirror is reflective for the control pump signal.

We describe an optomechanical device which fulfills the characteristicsfor non reciprocal transmission spectra in a silicon-silicon oxidematerial system. The device is shown in FIG. 27. The mirrors forming thecavity are created formed in a high index contrast system (refractiveindex of silicon 3.5, refractive index of oxide 1.5) using a quarterwave stack. The fabrication of the proposed device is straight forwardinvolving only lithography, etching, and deposition steps. A materialstack of silicon and oxide is etched from the oxide side to create theoptical cavity. Another silicon wafer is bonded to close the cavity,since there is no lithography involved on the second side of the cavitythere is no need for alignment of the mirrors. Polysilicon and oxide aredeposited to create Bragg reflectors with appropriate thickness. Themirror stack thicknesses are chosen such that probe is reflected at boththe mirrors while the pump is reflected only at the movable mirror (FIG.28). In the present design we consider a quarter wave stack of order 5at both the ends and a cavity length of 100 microns.

In FIG. 28 there is shown reflectivity spectra for the mirrors. The nonmovable mirror is transparent to the pump beam.

In FIG. 29 there is shown transmission spectrum of the device under noexcitation.

In FIG. 30 There is shown transmission spectrum of the device forforward and backward probe beam excitation. In FIG. 31 there is shown aclose up transmission spectra of the device for top (forward) and bottom(backward) incidence of pump beam. When light is incident from top, thecavity is blue shifted. When light is incident from bottom the cavity isred shifted. A shift of 10 nm is assumed consistent with the mechanicalsimulations.

In FIG. 32 there is shown a mechanical response of the movable mirror.

We also show an in-plane alternative to the proposed invention. In anin-plane device, add drop rings (one ring resonator side coupled to twowaveguides acts as a mirror by rerouting the incident light into thesecond waveguide. The net change of optical momentum exerts a force onthe structure. By suspending the cavities on a chip we can use an adddrop ring as a movable mirror. A second static mirror is created byanother add drop ring which is not suspended to keep the mirror static.The principle of operation of the mirror is exactly similar to thedescription above.

Other alternatives may use several photonic structures (for example,toroids, rings, photonic crystals, metallic mirrors) which act asreflectors. Any method of mechanical suspension can be integrated tocreate the movable cavity. The methods of suspension can be mechanical,electrical, optical, magnetic levitation, micro fluidic (air or liquid).

In FIG. 33 there is shown an in-plane alternative to the proposeddevice.

There are a number of possible uses for devices described herein.Devices described herein can sense presence of a strong optical beamforward or backward and produce distinguishable responses. Devicesdescribed herein also can act as an optical isolator for strong opticalsignals. Devices described herein also can avoid the use ofmagneto-optic media, optically active media, or photovoltaicelectrooptic crystals. Devices described herein also can act as asaturable absorber or a saturable power limiter. Devices describedherein also can act as a saturable absorber for use in pulses lasersystems. Devices described herein also can act as a safety measure toblock intense light for sensitive optical systems for safety purposes.Devices described herein also can be used as a light controlled lightswitch. Devices described herein also can be used for intra chip,chip-chip, rack-rack, and long haul data transmission as part of anelectronic, photonic, or electro-optic chip. Devices described hereinalso can be used in all packaged optical systems as a safety feature.Devices described herein also can be used to create military safety eyewear where strong laser beams from enemy laser weapon systems can beprevented from creating optical damage to soldiers and equipment byblocking strong light from one direction.

[End of Section Excerpted as Appendix A of U.S. Provisional PatentApplication No. 61/153,913]

[End of Excerpt Taken From U.S. Provisional Patent Application No.61/153,913]

A small sample of systems methods and apparatus that are describedherein is as follows:

-   A1. An optomechanical device comprising: a first mirror; and a    second mirror forming with the first mirror a cavity; wherein the    first mirror is a movable mirror; wherein the optomechanical device    is adapted so that the first mirror is moveable responsively to    radiation force.-   A2. The optomechanical device of A1, wherein the second mirror is a    stationary mirror.-   A3. The optomechanical device of A1, wherein the optomechanical    device includes a mechanical stop for stopping the first mirror.-   A4. The optomechanical device of A1, wherein the optomechanical    device includes a mechanical stop for stopping the first mirror at a    certain position to result in a certain resonance wavelength band of    the cavity being defined.-   A5. The optomechanical device of A1, wherein the optomechanical    device is operative so that light incident on the cavity in a    forward direction results in a first set of radiation forces on the    first mirror, and wherein the optomechanical device is further    operative so that light incident on the cavity in a backward    direction results in a second set of radiation forces on the first    mirror, the sum of the second set of radiation forces being    different from a sum of the first set of radiation forces.-   A6. The optomechanical device of A1, wherein the optomechanical    device is fabricated in a solid state material system. A7. The    optomechanical device A6, wherein the solid state material is    fabricated in a silicon material system.-   A8. The optomechanical device of A1, wherein the first mirror is    made moveable with use of mechanical suspensions.-   A9. The optomechanical device of A8, wherein the mechanical    suspensions are provided by cantilevers.-   A10. The optomechanical device of A1, wherein the optomechanical    device includes a light source that emits light at a certain central    wavelength, and wherein the optomechanical device is operative so    that light emitted from the light source incident on the cavity in a    forward direction results in a first set of radiation forces being    imparted on the first mirror, and wherein the optomechanical device    is further operative so that reflected light having the certain    central wavelength incident on the cavity in a backward direction    results in a second set of radiation forces being imparted on the    first mirror, wherein a sum of the first set of radiation forces,    and a sum of the second set of radiation forces are not equal so    that there is defined for the cavity a first resonance wavelength    band for light incident on the cavity in the forward direction and a    second resonance wavelength band for light incident on the cavity in    the backward direction.-   A11. The optomechanical device of A1, wherein the optomechanical    device includes a light source that emits light at a certain central    wavelength, and wherein the optomechanical device is operative so    that light emitted from the light source incident on the cavity in a    forward direction results in a first set of radiation forces being    imparted on the first mirror, and wherein the optomechanical device    is further operative so that reflected light having the certain    central wavelength incident on the cavity in a backward direction    results in a second set of radiation forces being imparted on the    first mirror, wherein a sum of the first set of radiation forces,    and a sum of the second set of radiation forces are not equal so    that there is defined for the cavity a first resonance wavelength    band for light incident on the cavity in the forward direction and a    second resonance wavelength band for light incident on the cavity in    the backward direction, wherein the certain central wavelength is    matched to the first resonance wavelength band but not matched to    the second resonance wavelength band so that the reflected light at    the certain central wavelength is not transmitted by the cavity.    A12. The optomechanical device of A1, wherein the optomechanical    device includes a light source that emits light at a certain central    wavelength, and wherein the optomechanical device is operative so    that light emitted from the light source incident on the cavity in a    forward direction results in a first set of radiation forces being    imparted on the first mirror, and wherein the optomechanical device    is further operative so that reflected light having the certain    central wavelength incident on the cavity in a backward direction    simultaneously with light from the light source being incident on    the cavity in the forward direction results in a second set of    radiation forces being imparted on the first mirror, wherein a sum    of the first set of radiation forces, and a sum of the second set of    radiation forces are not equal so that there is defined for the    cavity a first resonance wavelength band for light incident on the    cavity in the forward direction and a second resonance wavelength    band for light incident on the cavity in the backward direction    simultaneously with light from the light source being incident on    the cavity in the forward direction, wherein the certain central    wavelength is matched to the first resonance wavelength band but not    matched to the second resonance wavelength band so that the    reflected light at the certain central wavelength is not transmitted    by the cavity.-   A13. The optomechanical device of A1, wherein during an initial    state a resonance wavelength band of the cavity is matched to a    certain central wavelength so that the cavity is capable of    transmitting light emitted from a light source at the certain    central wavelength, and wherein the optomechanical device is adapted    so that a set of radiation forces on the first mirror attributable    to emission of light at the certain central wavelength with    sufficient power results in a resonance wavelength band of the    cavity shifting from a wavelength band at which the resonance    wavelength band of the cavity is matched to the certain central    wavelength to a wavelength band at which the resonance wavelength    band is not matched to the certain central wavelength.-   A14. The optomechanical device of A1, wherein during an initial    state a resonance wavelength band of the cavity is not matched to a    certain central wavelength so that in an initial state the cavity is    restricted from transmitting light emitted from a light source at    the certain central wavelength, and wherein the optomechanical    device is adapted so that a set of radiation forces on the first    mirror attributable to emission of light at the certain central    wavelength with sufficient power results in a resonance wavelength    band of the cavity shifting from a wavelength band at which the    resonance wavelength band of the cavity is not matched to the    certain central wavelength to a wavelength band at which the    resonance wavelength band of the cavity is matched to the certain    central wavelength.-   A15. The optomechanical device of A14, wherein the optomechanical    device includes a stop for stopping the first mirror at a certain    position for stabilization of the resonance wavelength band at a    wavelength band at which it is matched to the certain central    wavelength when light having the certain central wavelength of    sufficient power is incident on the cavity.-   A16. The optomechanical device of A1, wherein the optomechanical    device is adapted so that radiation force on the first mirror    attributable to emission of light of a certain central wavelength    with sufficient power results in a resonance wavelength band of the    cavity shifting between a first state in which a resonance    wavelength band of the cavity includes a set of wavelengths shorter    than a wavelength band matched to a certain central wavelength, a    second state in which a resonance wavelength band of the emitted    light is matched to a the certain central wavelength, and the third    state in which the resonance wavelength band of the cavity includes    a set of wavelengths longer than a wavelength band matched to the    certain central wavelength.-   A17. The optomechanical device of A1, wherein the optomechanical    device is configured so that the first mirror and the second mirror    are provided in a common plane.-   A18. The optomechanical device of A1, wherein the optomechanical    device includes an in-plane device structure.-   A19. The optomechanical device of A1, wherein the optomechanical    device is configured as an eyewear apparatus.-   A20. The optomechanical device of A1, wherein the optomechanical    device is configured as an eyewear apparatus, the eyewear apparatus    having an eyewear apparatus frame that supports the cavity. B1. An    optomechanical device comprising: a light source; a first mirror;    and a second mirror forming with the first mirror a cavity; wherein    the first mirror is a movable mirror; wherein the optomechanical    device is adapted so that the first mirror is moveable responsively    to radiation force; wherein the light source emits light at a    certain central wavelength, and wherein the optomechanical device is    operative so that light emitted from the light source incident on    the cavity in a forward direction results in a first set of    radiation forces being imparted on the first mirror, and wherein the    optomechanical device is further operative so that reflected light    having the certain central wavelength incident on the cavity in a    backward direction results in a second set of radiation forces being    imparted on the first mirror, wherein a sum of the first set of    radiation forces, and a sum of the second set of radiation forces    are not equal so that there is defined for the cavity a first    resonance wavelength band for light incident on the cavity in the    forward direction and a second resonance wavelength band for light    incident on the cavity in the backward direction.-   C1. An optomechanical device comprising: a light source; a first    mirror; and a second mirror forming with the first mirror a cavity;    wherein the first mirror is a movable mirror; wherein the    optomechanical device is adapted so that the first mirror is    moveable responsively to radiation force; wherein the light source    emits light at a certain central wavelength, and wherein the    optomechanical device is operative so that light emitted from the    light source incident on the cavity in a forward direction results    in a first set of radiation forces being imparted on the first    mirror, and wherein the optomechanical device is further operative    so that reflected light having the certain central wavelength    incident on the cavity in a backward direction simultaneously with    light from the light source being incident on the cavity in the    forward direction results in a second set of radiation forces being    imparted on the first mirror, wherein a sum of the first set of    radiation forces, and a sum of the second set of radiation forces    are not equal so that there is defined for the cavity a first    resonance wavelength band for light incident on the cavity in the    forward direction and a second resonance wavelength band for light    incident on the cavity in the backward direction simultaneously with    light from the light source being incident on the cavity in the    forward direction, wherein the certain central wavelength is matched    to the first resonance wavelength band but not matched to the second    resonance wavelength band so that the reflected light at the certain    central wavelength is not transmitted by the cavity.-   D1. An optomechanical device comprising: a first mirror; and a    second mirror forming with the first mirror a cavity; wherein the    first mirror is a movable mirror; wherein the optomechanical device    is adapted so that the first mirror is moveable responsively to    radiation force; wherein during an initial state a resonance    wavelength band of the cavity is matched to a certain central    wavelength so that the cavity is capable of transmitting light    emitted from a light source that emits light at the certain central    wavelength, and wherein the optomechanical device is adapted so that    a set of radiation forces on the first mirror attributable to    emission of light at the certain central wavelength with sufficient    power results in a resonance wavelength band of the cavity shifting    from a wavelength band at which the resonance wavelength band of the    cavity is matched to the certain central wavelength to a wavelength    band at which the resonance wavelength band is not matched to the    certain central wavelength.-   E1. An optomechanical device comprising: a first mirror; and a    second mirror forming with the first mirror a cavity; wherein the    first mirror is a movable mirror; wherein the optomechanical device    is adapted so that the first mirror is moveable responsively to    radiation force; wherein during an initial state a resonance    wavelength band of the cavity is not matched to a certain central    wavelength so that in an initial state the cavity is restricted from    transmitting light emitted from a light source that emits light at    the certain central wavelength, and wherein the optomechanical    device is adapted so that a set of radiation forces on the first    mirror attributable to emission of light at the certain central    wavelength with sufficient power results in a resonance wavelength    band of the cavity shifting from a wavelength band at which the    resonance wavelength band of the cavity is not matched to the    certain central wavelength to a wavelength band at which the    resonance wavelength band of the cavity is matched to the certain    central wavelength.-   F1. A method comprising: providing an optomechanical device, the    optomechanical device being adapted so that forward incident light    results in a first set of radiation forces being imparted to    optomechanical device, the optomechanical device further being    adapted so that backward incident light results in a second set of    radiation forces being imparted to the optomechanical device, the    optomechanical device having a first transmittivity band when the    first set of forces are imparted to the optomechanical device, the    optomechanical device having a second transmittivity band when the    second set of forces are imparted to the optomechanical device; and    directing light toward the optomechanical device at a central    wavelength matching the first transmittivity band.-   F2. The method of F1, wherein the providing step includes the step    of providing a cavity.-   F3. The method of F1, wherein the providing step includes the step    of providing a cavity having a moveable mirror.-   F4. The method of F3, wherein the providing step further includes    providing a stop for stopping the moveable mirror at a certain    position for stabilization of a current transmittivity band of the    optomechanical device.-   F5. The method of F1, wherein the method further includes the step    of blocking reflected light transmitted by the optomechanical device    utilizing the optomechanical device.

While the present invention has been described with reference to anumber of specific embodiments, it will be understood that the truespirit and scope of the invention should be determined only with respectto claims that can be supported by the present specification. Further,while in numerous cases herein wherein systems and apparatuses andmethods are described as having a certain number of elements it will beunderstood that such systems, apparatuses and methods can be practicedwith fewer than or greater than the mentioned certain number ofelements. Also, while a number of particular embodiments have beendescribed, it will be understood that features and aspects that havebeen described with reference to each particular embodiment can be usedwith each remaining particularly described embodiment.

We claim:
 1. An optomechanical device comprising: a first mirror; and asecond mirror forming with the first mirror a cavity; wherein the firstmirror is a movable mirror; wherein the optomechanical device is adaptedso that the first mirror is moveable responsively to radiation force;wherein the optomechanical device includes a mechanical stop forstopping the first mirror at a certain position to result in a certainresonance wavelength band of the cavity being defined; and wherein theoptomechanical device is operative so that light incident on the cavityin a forward direction results in a first set of radiation forces on thefirst mirror, and wherein the optomechanical device is further operativeso that reflected light transmitted through the cavity incident on thecavity in a backward direction results in a second set of radiationforces on the first mirror, a sum of the second set of radiation forcesbeing different from a sum of the first set of radiation forces.
 2. Theoptomechanical device of claim 1, wherein the first mirror is mademoveable with use of mechanical suspensions.
 3. The optomechanicaldevice of claim 2, wherein the mechanical suspensions are provided bycantilevers.
 4. The optomechanical device of claim 1, wherein the secondmirror is a stationary mirror.
 5. The optomechanical device of claim 1,wherein the first mirror includes a photonic crystal.
 6. Theoptomechanical device of claim 1, wherein the first mirror includes aphotonic crystal and wherein the second mirror includes a photoniccrystal.
 7. The optomechanical device of claim 1, wherein theoptomechanical device includes an in-plane device structure.
 8. Theoptomechanical device of claim 1, wherein the optomechanical device isconfigured so that the first mirror and the second mirror are providedin a common plane.
 9. The optomechanical device of claim 8, wherein thefirst mirror and the second mirror have respective planar structuresthat extend in a common plane.
 10. The optomechanical device of claim 8,wherein the first mirror and the second mirror extend in a common plane.11. The optomechanical device of claim 8, wherein the first mirror andthe second mirror are disposed side by side and extend in a commonplane.
 12. The optomechanical device of claim 8, wherein theoptomechanical device defines a cavity provided as an in-planeoptomechanical device having an in-plane device structure.
 13. Theoptomechanical device of claim 1, wherein the mechanical stop is spacedapart from the first mirror.
 14. The optomechanical device of claim 1,wherein the mechanical stop is adapted for stopping movement of thefirst mirror in one direction.
 15. The optomechanical device of claim 1,wherein the mechanical stop is adapted to stop movement of the firstmirror in a first direction, and wherein the optomechanical device isadapted so that the first mirror is free to move in a second directionopposite the first direction without being stopped by a mechanical stop.16. The optomechanical device of claim 1, wherein during an initialstate a resonance wavelength band of the cavity is not matched to acertain central wavelength so that in an initial state the cavity isrestricted from transmitting light emitted from a light source at thecertain central wavelength, and wherein the optomechanical device isadapted so that a set of radiation forces on the first mirrorattributable to emission of light at the certain central wavelength withsufficient power results in a resonance wavelength band of the cavityshifting from a wavelength band at which the resonance wavelength bandof the cavity is not matched to the certain central wavelength to awavelength band at which the resonance wavelength band of the cavity ismatched to the certain central wavelength.
 17. The optomechanical deviceof claim 1, wherein the mechanical stop is provided to include a dampedresponse.
 18. The optomechanical device of claim 1, wherein themechanical stop is provided to include a damped response withoutoscillation.
 19. The optomechanical device of claim 1, wherein themechanical stop is resistant to adhering with externally disposedobjects.
 20. The optomechanical device of claim 1, wherein themechanical stop includes a polymer coating so that the mechanical stopis resistant to adhering with externally disposed objects.
 21. Theoptomechanical device of claim 1, wherein the optomechanical deviceincludes a light source emitting light at a certain central wavelengthand wherein the certain position is a position for stabilization of theresonance wavelength band at a wavelength band at which it is matched tothe certain central wavelength.
 22. The optomechanical device of claim1, wherein the optomechanical device includes a light source emittinglight at a certain central wavelength and wherein the certain positionis a position for stabilization of the resonance wavelength band at awavelength band at which it is matched to the certain central wavelengthso that forward directed light emitted by the light source and incidenton the cavity is transmitted through the cavity.
 23. The optomechanicaldevice of claim 1, wherein the optomechanical device includes a lightsource that emits light at a certain central wavelength, and wherein theoptomechanical device is operative so that light emitted from the lightsource incident on the cavity in a forward direction results in thefirst set of radiation forces being imparted on the first mirror, andwherein the optomechanical device is further operative so that reflectedlight transmitted through the cavity having the certain centralwavelength incident on the cavity in a backward direction results in thesecond set of radiation forces being imparted on the first mirror,wherein a sum of the first set of radiation forces, and a sum of thesecond set of radiation forces are not equal so that there is definedfor the cavity a first resonance wavelength band for light incident onthe cavity in the forward direction and a second resonance wavelengthband for light incident on the cavity in the backward direction.
 24. Theoptomechanical device of claim 1, wherein the optomechanical deviceincludes a light source that emits light at a certain centralwavelength, and wherein the optomechanical device is operative so thatlight emitted from the light source incident on the cavity in a forwarddirection results in the first set of radiation forces being imparted onthe first mirror, and wherein the optomechanical device is furtheroperative so that reflected light transmitted through the cavity havingthe certain central wavelength incident on the cavity in a backwarddirection results in a the second set of radiation forces being impartedon the first mirror, wherein a sum of the first set of radiation forces,and a sum of the second set of radiation forces are not equal so thatthere is defined for the cavity a first resonance wavelength band forlight incident on the cavity in the forward direction and a secondresonance wavelength band for light incident on the cavity in thebackward direction, wherein the certain central wavelength is matched tothe first resonance wavelength band but not matched to the secondresonance wavelength band so that the reflected light at the certaincentral wavelength is not transmitted by the cavity.
 25. Theoptomechanical device of claim 1, wherein the optomechanical deviceincludes a light source that emits light at a certain centralwavelength, and wherein the optomechanical device is operative so thatlight emitted from the light source incident on the cavity in a forwarddirection results in the first set of radiation forces being imparted onthe first mirror, and wherein the optomechanical device is furtheroperative so that reflected light transmitted through the cavity havingthe certain central wavelength incident on the cavity in a backwarddirection simultaneously with light from the light source being incidenton the cavity in the forward direction results in the second set ofradiation forces being imparted on the first mirror, wherein a sum ofthe first set of radiation forces, and a sum of the second set ofradiation forces are not equal so that there is defined for the cavity afirst resonance wavelength band for light incident on the cavity in theforward direction and a second resonance wavelength band for lightincident on the cavity in the backward direction simultaneously withlight from the light source being incident on the cavity in the forwarddirection, wherein the certain central wavelength is matched to thefirst resonance wavelength band but not matched to the second resonancewavelength band so that the reflected light at the certain centralwavelength is not transmitted by the cavity.
 26. The optomechanicaldevice of claim 1, wherein during an initial state a resonancewavelength band of the cavity is matched to a certain central wavelengthso that the cavity is capable of transmitting light emitted from a lightsource at the certain central wavelength, and wherein the optomechanicaldevice is adapted so that a set of radiation forces on the first mirrorattributable to emission of light at the certain central wavelength withsufficient power results in a resonance wavelength band of the cavityshifting from a wavelength band at which the resonance wavelength bandof the cavity is matched to the certain central wavelength to awavelength band at which the resonance wavelength band is not matched tothe certain central wavelength.
 27. The optomechanical device of claim16, wherein the optomechanical device includes the mechanical stop forstopping the first mirror at a certain position for stabilization of theresonance wavelength band at a wavelength band at which it is matched tothe certain central wavelength when light having the certain centralwavelength of sufficient power is incident on the cavity.
 28. Theoptomechanical device of claim 1, wherein the optomechanical device isadapted so that radiation force on the first mirror attributable toemission of light of a certain central wavelength with sufficient powerresults in a resonance wavelength band of the cavity shifting between afirst state in which a resonance wavelength band of the cavity includesa set of wavelengths shorter than a wavelength band matched to a certaincentral wavelength, a second state in which a resonance wavelength bandof the cavity is matched to a the certain central wavelength, and athird state in which the resonance wavelength band of the cavityincludes a set of wavelengths longer than a wavelength band matched tothe certain central wavelength.
 29. The optomechanical device of claim1, wherein the first mirror is provided by a drop ring.
 30. Theoptomechanical device of claim 1, comprising a waveguide opticallycoupled to a set of edges of the first mirror and the second mirror. 31.The optomechanical device of claim 1, wherein the optomcchanical deviceconfigured so that the first mirror and the second mirror are providedin a common plane, and wherein the optomechanical device includes awaveguide optically coupled to a set of edges of the first mirror andthe second mirror.
 32. The optomechanical device of claim 1, comprisinga first waveguide optically coupled to a first set of edges of the firstmirror and the second mirror and a second waveguide optically coupled toa second set of edges of the first mirror and the second mirror.
 33. Theoptomechanical device of claim 1, wherein the optomechanical device isfabricated in a solid state material system.
 34. The optomechanicaldevice of claim 1, wherein the optomechanical device is configured as aneyewear apparatus.
 35. The optomechanical device of claim 1, wherein theoptomechanical device is configured as an eyewear apparatus, the eyewearapparatus having an eyewear apparatus frame that supports the cavity.36. An optomechanical device comprising: a light source; a first mirror;and a second mirror forming with the first mirror a cavity; wherein thefirst mirror is a movable mirror; wherein the optomechanical device isadapted so that the first mirror is moveable responsively to radiationforce; wherein the light source emits light at a certain centralwavelength, and wherein the optomechanical device is operative so thatlight emitted from the light source incident on the cavity in a forwarddirection results in a first set of radiation forces being imparted onthe first mirror, and wherein the optomechanical device is furtheroperative so that reflected light transmitted through the cavity havingthe certain central wavelength incident on the cavity in a backwarddirection results in a second set of radiation forces being imparted onthe first mirror, wherein a sum of the first set of radiation forces,and a sum of the second set of radiation forces are not equal so thatthere is defined for the cavity a first resonance wavelength band forlight incident on the cavity in the forward direction and a secondresonance wavelength band for light incident on the cavity in thebackward direction.
 37. The optomechanical device of claim 36, whereinthe optomechanical device includes a mechanical stop for stoppingmovement of the first mirror in a first direction, wherein theoptomechanical device is configured so that the first mirror and thesecond mirror are provided in a common plane, and wherein theoptomechanical device includes a waveguide optically coupled to a set ofedges of the first mirror and the second mirror.
 38. An optomechanicaldevice comprising: a light source; a first mirror; and a second mirrorforming with the first mirror a cavity wherein the first mirror is amovable mirror; wherein the optomechanical device is adapted so that thefirst mirror is moveable responsively to radiation force; wherein thelight source emits light at a certain central wavelength, and whereinthe optomechanical device is operative so that light emitted from thelight source incident on the cavity in a forward direction results in afirst set of radiation forces being imparted on the first mirror, andwherein the optomechanical device is further operative so that reflectedlight transmitted through the cavity having the certain centralwavelength incident on the cavity in a backward direction simultaneouslywith light from the light source being incident on the cavity in theforward direction results in a second set of radiation forces beingimparted on the first mirror, wherein a sum of the first set ofradiation forces, and a sum of the second set of radiation forces arenot equal so that there is defined for the cavity a first resonancewavelength band for light incident on the cavity in the forwarddirection and a second resonance wavelength band for light incident onthe cavity in the backward direction simultaneously with light from thelight source being incident on the cavity in the forward direction,wherein the certain central wavelength is matched to the first resonancewavelength band but not matched to the second resonance wavelength bandso that the reflected light at the certain central wavelength is nottransmitted by the cavity.
 39. An optomechanical device comprising: afirst mirror; and a second mirror forming with the first mirror acavity; wherein the first mirror is a movable mirror; wherein theoptomechanical device is adapted so that the first mirror is moveableresponsively to radiation force; wherein the optomechanical deviceincludes a light source that emits light at a certain centralwavelength, and wherein the optomechanical device is operative so thatlight emitted from the light source incident on the cavity in a forwarddirection results in a first set of radiation forces being imparted onthe first mirror, and wherein the optomechanical device is furtheroperative so that reflected light having the certain central wavelengthincident on the cavity in a backward direction simultaneously with lightfrom the light source being incident on the cavity in the forwarddirection results in a second set of radiation forces being imparted onthe first mirror, wherein a sum of the first set of radiation forces,and a sum of the second set of radiation forces are not equal so thatthere is defined for the cavity a first resonance wavelength band forlight incident on the cavity in the forward direction and a secondresonance wavelength band for reflected light transmitted through thecavity incident on the cavity in the backward direction simultaneouslywith light from the light source being incident on the cavity in theforward direction, wherein the certain central wavelength is matched tothe first resonance wavelength band but not matched to the secondresonance wavelength band so that the reflected light at the certaincentral wavelength is not transmitted by the cavity.
 40. Theoptomechanical device of claim 39, wherein the optomechanical deviceincludes a mechanical stop for stopping the first mirror at a certainposition to result in the first resonance wavelength band of the cavitybeing defined.